Biological Prerequisites for Aquaculture

Stuart J. Rowland, Biologist, Grafton Aquaculture Centre


On a worldwide basis, aquacultural production has increased rapidly over the last two decades.

World production is made up of finfish, seaweed, molluscs and crustaceans. The majority of finfish are farmed in freshwater ponds. Some of the main fishes cultured for human consumption are: carp (several species, mainly Hypophthalmichthys molitrix and Gypfinns carpio), channel catfish (Ictalurus punctatus), Tilapia spp., eels (Anguilla spp.), milkfish (Chanos chanos), rainbow trout (Oncorhynchus mykiss) and salmon (Salmo salar).

This information describes the biological prerequisites of finfish for aquaculture; most of these prerequisites also apply to crustaceans. Failure to meet one or more of these prerequisites may make a species unsuitable for aquaculture.

Established hatchery techniques

Large numbers of larvae, fry or juveniles must be available for grow-out operations. In Australia, aquaculturists are generally not permitted to collect juveniles from the wild (which is an unreliable source); therefore hatcheries are the only source of seed for grow-out operations. Broodfish must be available to establish successful hatchery techniques; the species should be fecund and capable of spawning in captivity.


Cultivated species must thrive in captivity and be amenable to crowding. The more fish that can be stocked into a given space, the greater the potential production.

Suitable behavior

Regular observation and sampling of fish are essential for successful culture; fish that are readily seen and/or easily captured are desirable. Species that school and swim near the surface or edges are ideal, as are species that can be readily trained to feed at a particular area. Species that are very flighty or secretive are usually less suitable for aquaculture.

Rapid and uniform growth

Species must be capable of rapid growth to ensure efficient use of facilities and food. Most species of finfish that are farmed successfully throughout the world grow rapidly under culture conditions and reach minimum market size (500grams) in 18 months or less.

Variable growth amongst fish within a rearing unit is undesirable as it necessitates culling or grading, which increases stress and susceptibility to disease, damage to the fish, and requires extra labour and facilities.

Amenable to artificial feeding

Semi-intensive and intensive fish culture is based on the use of medium to high stocking densities, prepared feeds (usually specially formulated pellets) and with some species, fertilisation of pond water. Very high production rates can only be achieved with species that accept prepared feed.

Appropriate dietary requirements

In general, fish that feed lower in the food chain are most efficient in the use of food under pond culture conditions. Although some carnivorous species accept artificial feeds, they require relatively high levels of protein (including animal proteins) and are unable to use most of the natural food available in ponds.

Efficient food conversion

The food conversion ratio (FCR) is the ratio of dry weight of food, to the wet weight gain of fish. The lower the ratio, the more efficiently food has been converted to fish flesh. Feed costs often constitute 40-60% of total production costs, so it is essential to use species that convert food efficiently. Modern dry pellet diets enable food conversion ratios of 2:1 (2 kg food fed to 1 kg fish produced) or better.


Cannibalism reduces survival rate and production directly by predation or, indirectly through damage and increased stress-related susceptibility to disease. The greater the degree of cannibalism, the greater the losses. Most piscivorous and many carnivorous species can be cannibalistic and must be culled to reduce losses. Culling is generally undesirable for reasons discussed earlier.

Disease resistance

Although all species are susceptible to diseases under culture conditions, some are more so than others. This factor should be considered when selecting a species for aquaculture or choosing the site for grow-out operations.


Although good water quality is essential for successful culture, species that can tolerate sub-optimal conditions (for example, high or low temperatures, low dissolved oxygen, high pH) for short periods are more suitable than less tolerant species.

High meat recovery

Species that have high meat to total body weight ratio are desirable because of their more efficient conversion of feed into edible flesh. This is particularly important if the end product is to be processed.


In addition to these biological factors, a species must have high market acceptance. The ultimate goal of commercial aquaculture is to make a profit; the farmer must produce fish that are marketable in sufficient quantities at acceptable prices. The more marketable the fish, the greater the chance of establishing an economically viable enterprise. In determining the potential of a species for aquaculture, one of the first steps is to determine and evaluate the marketability of the species.


For further information, call NSW DPI Port Stephens Fisheries Centre on 02 4982 1232